Imagine that you’ve just returned from your dream beach holiday, and it was glorious. But now it’s over, and you’re feeling a little bit irritable, bloated and sleepy. You’re probably suffering from jet lag.
Horace Sutton made the first mention of the term jet lag in 1966 in the Los Angeles Times. He says that “Jets travel so fast that they leave your body rhythms behind,” and he was pretty close to the mark.
Circadian clocks govern human bodies. These clocks keep our internal systems in an almost precisely 24-hour repeating pattern. This means that our body has a good sense of “when it’s time to get up” and “when it’s time to go to sleep.” It has a rhythm. Suppose I meant to take my body and send it from London to Los Angeles. What was bedtime in London is now mid-afternoon, and my body is effectively eight hours out of whack.
Your body’s rhythm is good at regulating itself, but it responds to external cues such as sunlight. Changes in light trigger your body to release melatonin which is the sleep hormone. To understand this process, we have to start with our eyes. Our eyes have three types of light-sensitive cells; rods, cones, and photosensitive ganglion cells.
The first two are well known for allowing us to see, but it’s the third type we’re interested in here because they affect our circadian rhythms. Photosensitive ganglion cells can detect how bright it is and let our circadian clock know whether it’s day or night based on that. When light hits these cells, they absorb photons and release neurotransmitters. The neurotransmitters trigger nerve impulses that travel directly into the suprachiasmatic nucleus, which is the brain’s region that acts as our circadian clock. The clock interprets the pulses and, if necessary, signals the pineal gland that it’s time to start secreting melatonin.
Scientists have shown that you can shift your body’s rhythm by one to two hours using light without physical side effects. So how can we use this information to help us counter the effects of jet lag? All we need to do is pre-adjust our body’s internal clock which is pretty simple.
For example, if I’m traveling east, all I need to do is go to bed one hour earlier than I usually would two days before I travel. I also need to seek bright lights in the morning because light and jet lag is connected. It is because light triggers our body’s melatonin sleep hormone. One day before I travel, I need to increase this by one hour. So, instead of going to bed at my usual time, I’m going to bed two hours before that. If I keep changing this by adding an hour every day, even when I’m traveling until I get to my usual sleep time, and then I can stop. If I am going west, all I do is do the opposite. By doing this, I can significantly reduce, if not eliminate, the effects of jet lag.
You might hate jet lag, but actually, but it’s just a temporary issue for us that comes up whenever we go on holiday. Spare a thought for astronauts because for astronauts, and this is potentially a huge headache. Future Mars colonists will need to use training methods like those I’ve just given you to prepare their bodies because at 24.65, the Mars days just long enough to knock their bodies off-kilter.